The Iterative Spectrally Smooth Temperature-Emissivity Separation algorithm (ISSTES) is an inversion method for retrieving surface temperature and emissivity from remotely sensed hyperspectral thermal infrared radiance. It is important to quantify the error sensitivity for ISSTES—this is needed by system designers in determining system parameters required for a given retrieval error, and is also needed by consumers of the temperature/emissivity products as an indicator of product quality.